/Engine/Source/Developer/IoStoreUtilities/Public/ZenStoreWriter.h
Cooked package writers asynchronously hash the chunks for each package after CommitPackage. Once cooking has completed, use this to acquire the results. This is synced using voidUPackage::WaitForAsyncFileWrites()- do not access the results before that completes. Non-const so that the cooking process can Move the map of hashes.
virtual [TMap](API\Runtime\Core\Containers\TMap)< [FName](API\Runtime\Core\UObject\FName), [TRefCountPtr](API\Runtime\Core\Templates\TRefCountPtr)< [FPackageHashes](API\Runtime\Core\Serialization\FPackageHashes) > > & GetPackageHashes()